Drilling fluid for combating heaving shale



ossiea DRILLING FLUID FOR COMBATING HEAG SHALE George E. Cannon, Houston, Tex, assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application September 18, 1937, Serial No. 164,495

6 Claims. (Cl. 255-1) This invention relates to a drilling fiuid which It is to be understood that it is not possible will efiect a minimum of disintegration of heavto fix absolute limits upon the amount of the ing shale. addition agent to be employed. The most efiec- In the rotary drilling of oil and gas wells 2. tive amount must usually be determined by ex- 5 mud fluid is pumped down the drill stem to the perimentation, that is, by obtaining a sample of drill at the working face in the bottom of the heaving shale through which the drilling is to bore. The stream of mud fluid passes across the be done and observing its rate and degree of disworking face of the drill and escapes upward integration by the action of water containing through the bore. In some areas, notably the various concentrations of the addition agent.

Gulf Coast of Texas and Louisiana, a formation In some cases it may be found that less than known as heaving shale must be penetrated in the minimum proportion of addition agent given certain wells. It is difiicult and often impossible above will be sufilcient. In extreme cases it may to penetrate this formation by ordinary rotary be necessary to add as much as 75% or 80%, by drilling methods and mud fluids. This shale has weight, of the addition agent.

a tendency to move into the hole filling up the In carrying out the preferred embodiment of 15 hole already drilled, and often sticking the drillthe present invention a well is drilled through ing tools. It is believed that the cause of this the ordinary earth formations using the conaction is due to the hydration of the shale parventional aqueous mud of suitable weight, which ticles by the water contained in ordinary drilling may be from 8-18 lbs. per gallon. When the $0 muds. A heaving shale may be defined as one drill approaches a sub-stratum composed of which in contact with the ordinary drilling mud heaving shale, a polyhydroxy organic compound swells or disintegrates spontaneously so much as of the type described above is added in the preto interfere with the drilling operation. scribed proportions and the drilling is continued In accordance with the present invention, the through the heaving shale. In some cases it may disintegration of a heaving shale is prevented be desired to make up a special mud for the heav- 25 by the addition to an ordinary drilling mud of ing shale instead of merely adding the polyhyvarying amounts of a water soluble, polyhydroxy droxy compound to the mud at hand. alcohol or saccharose, preferably one which con- The addition agents employed according to talns three or more hydroxyl. groups. By ordinary the present invention are not electrolytes and,

39 drilling mud is meant the usual drilling mud used consequently, do notcorrode the drilling equip- Q0 in rotary drilling which is comprised usually of ment. By virtue of the plurality of hydroxyl clays encountered during the drilling operation, groups contained in these agents they aid in mixed with water. The drilling mud may conmaintaining the clay and weighting material in tain weighting materials or colloidal addition suspension in the water. Moreover, these addimaterials. tion agents increase the viscosity of the drilling Among the organic addition agents which may mud as well as its density, and, thereby, reduce be employed are the glycols, glycerol, sor'bitol, losses of the drilling fluid into sub-surface erythrltol, sucrose, starch and dextrin. Of formations. these, glycerol is preferred. The organic com- The nature and objects of the present inven- 40 pound used need not be pure. When it occurs tion having been thus described what is claimed 49 in nature, such as in vegetable matter, an extract as new and useful and is desired to be secured of the vegetable matter containing it is suitable. by L tt r P t nt, 1

The addition agent should be used in an 1. A drilling fluid comprising a suspension of amount of at least by weight. of the mud clay in a mixture of water and glycerol. a d. p rably, 40% or more. In the case of liq- 2. A drilling mud comprising a suspension of 45 uid addition a en s. h amount o be added may clay in water containing at least 20%, by weight, be expressed volumetrlcally as at least 15% and, of glycerol.

preferably, 30% or more. In the case of glycerol, 3. A drilling fluid comprising a suspension of excellent results have been obtained by using clay in water containing more than by 50 muds containing 40-60, by volume, of glycerol v lume, of glycerol. 5:0 with respect to the water present. 4. A drilling fluid, according to claim 1, con

The action of these polyhydroxy addition taining caustic soda. agents is improved by the simultaneous addition 5. A drilling fluid comprising a suspension of of caustic soda. Enough caustic soda to make a clay' in a 5% solution of caustic soda containing 5% solution with the water present in the mud glycerol. imparts a noticeable improvement. Disintegra- 6. A drilling fluid comprising a suspension of tion of heaving shale has been wholly avoided clay in a 10% water solution oi caustic soda by the use of a mixture containing 40%, by containing more than 40%, by volume, of

volume, of glycerol and of a 10% water soluglycerol. so tion of caustic soda.

GEGRGE E CAIW QE-E. Q9 

